FRIDAY, Aug. 28 (HealthDay News) -- The latest results from the longest-running study yet confirm that surgery is better than artery-opening angioplasty in preventing strokes caused by blockage of the carotid artery, the largest vessel carrying blood to the brain.

"In contrast with endovascular treatment [angioplasty], surgical patients had about half the rate of strokes in long-term follow-up," said Dr. Martin M. Brown, a professor of stroke medicine at University College London Institute of Neurology, and a senior author of two reports in the October issue of the Lancet Neurology.

Brown is a leader of the so-called CAVATAS study, which has followed 504 people with carotid artery stenosis -- narrowing -- who were randomly assigned to have either the surgical procedure called endarterectomy or angioplasty.

"This was the first trial ever started comparing endovascular treatment with surgery," Brown said. Some participants in the trial have been followed for as long as eight years.

Carotid surgery is not a major operation, because the artery is close to the surface of the neck. It sometimes is done under local anesthesia. The surgeon clamps the artery shut and cuts fatty deposits from its wall. Angioplasty uses an inflatable balloon to improve blood flow.

One of the reports said there were more minor strokes in the 30 days after treatment in the angioplasty group than in the surgery group. The incidence of strokes, as well as the mini-strokes called transient ischemic attacks (TIAs), was higher in the angioplasty group over the next eight years -- 19.3 percent, compared to 17.2 percent in the surgery group.

But the number of people in the trial was small, so confirmation of the findings are needed from larger trials that are now in progress, the report said.

The second study reported on 413 CAVATAS participants who had periodic ultrasound examinations of the treated carotid arteries over the following five years. The study found that the incidence of severe re-narrowing of the carotid artery was much higher in the angioplasty group -- 31 percent over five years, compared to 11 percent in those who had surgery. Strokes or TIAs occurred in 23 percent of those who had severe re-narrowing, compared to 11 percent of those who didn't.

Implanting a stent -- a flexible tube that helps keep the artery open -- did reduce the incidence of blockage by about half in those who had angioplasty. But the overall superiority of surgery in reducing the risk of stroke was clear, the study authors said.

The CAVATAS results reinforce those of trials with shorter follow-ups, said Dr. Peter M. Rothwell, a professor of clinical neurology at the University of Oxford, who wrote an accompanying commentary in the journal.

"Taken together, all of the trials now show a substantially higher stroke risk associated with endovascular treatment compared to surgery," Rothwell said.

The findings apply only to people who have symptoms -- such as temporary loss of vision or speech -- because of carotid narrowing, Brown noted. Symptomless carotid stenosis sometimes is detected in the course of a routine physical examination, and the decision on whether to treat, and the appropriate treatment, is then up to the physician and patient, he said.

"In North America, most physicians would recommend surgery," Brown said. "In the United Kingdom, they are much more reluctant to operate on patients and would recommend medical treatment."

That medical treatment would include drugs to control high blood pressure and high blood cholesterol, as well as lifestyle changes, he said.

The difference in treatment choice is not due to the nationalized health care system in Britain, Brown said. Rather, "in the British system you do not see a surgeon unless you see a physician first. In the United States, many patients go straight to the surgeon," he said.

There are many surgeons in the United States, and "patients in the United States are more likely to want to have something done at once," he added.

There is still a place for angioplasty in the treatment of carotid stenosis, Rothwell said. After an initial diagnosis, some people prefer not to have surgery, he said.